Agricultural balers gather, compress, and shape crop material into a bale. There are different types of balers which create rectangular or square bales or cylindrical or round bales. Bales can be bound with netting, strapping, wire, or twine. A baler that produces small rectangular bales is often referred to as a square baler. Another type of baler is one that produces large rectangular bales, often referred to as large square baler.
Large square balers have been used in crop harvesting for many years. One advantage over other types of balers is that they densify the crop into large rectangular shaped bales, which can minimize shipping and storage costs. Large square balers usually utilize a compression system including a gearbox with a fixed length crank arm and a fixed length connecting rod which is attached to a plunger. During each rotation of the crank arm, the plunger compresses the crop in a baling chamber by extruding the crop though a rectangular chute as the plunger moves towards the rear of the baler. Crop is usually metered from a pre-compression chamber into the baler chamber. One purpose for having a pre-compression chamber is to collect enough crop material to make a full flake of hay prior to moving the crop in front of the plunger to be compressed.
One of the problems with a fixed length connecting rod is that a large amount of torque is required to get the flywheel, driveline components, gearbox components, and plunger to begin moving during startup of the baler. This problem is aggravated for balers that are capable of producing high density bales because these balers incorporate excessively large flywheels, more massive plungers, and heavier driveline components. This is also a problem when starting up a baler after it is plugged because the tractor must not only overcome the torque to get the components moving, but it also must overcome the additional torque that occurs as the plunger compresses crop that resides in the bale chamber.